A Risk Factor Analysis of Chronic Pleuritis in Danish Slaughter Pig Herds

Respiratory disease is considered the most serious disease problem in modern pig production and the risk has increased with the intensification of the pig production [1] Respiratory disease influence the general health status and production economy of the pig herds. Chronic pleuritis (CP), as an indicator of respiratory disease, is the most common finding at the post mortem meat inspection, accounting for approximately 70% of all recordings and with an overall prevalence of 24% of all pigs slaughtered in Denmark in 1998 [2]. The present study investigated and quantified risk factors for CP in Danish pig herds from the following 4 risk factor groups: herd and herd owner characteristics, management and neighbourhood factors. This combination of risk factors have not been analysed before in relation to Danish slaughter pig herds. Especially management factors are important to identify and quantify, in order to take preventive measures against respiratory disease, as they can alter the prevalence of respiratory disease in herds otherwise exposed equally [1, 3]. In the present study, the occurrence of CP was investigated in 544.299 slaughter pigs from 259 farrow to finisher or finishing herds at the mandatory post mortem meat inspection on 21 abattoirs in Denmark in the period from January to August 2000, inclusive. The monthly prevalences of CP were estimated as the percentage pigs with detected CP slaughtered at a specific abattoir in a specific month. Data were obtained from databases at the Danish Bacon and Meat Council and from telephone interviews based on a questionnaire. Data were analysed using a mixed model, PROC MIXED, SAS, and taking the correlation structures due to the repeated measurements of monthly CP prevalences into account. The resulting model showed the following factors to be associated with increased prevalence of CP: low health status opposed to a herd with a high health status, pig density in a 5 kilometre radius, mingling of pigs during the production period and month of slaughter. Whereas feeding with only dry feed and practising all in all out production were protective of CP. The study demonstrated that management factors can preventively influence the prevalence of CP and thereby the health status of pig herds and that management factors outweighs the influence of herd size.